Methods of operating a pump to reduce or eliminate pump backlash errors

ABSTRACT

A method of operating a pump can include advancing a stepper motor one or more additional steps in a first direction after detecting a first change in a limit sensor state corresponding to a piston reaching an end of its travel in a first direction. After advancing the stepper motor the additional step or steps in the first direction, the stepper motor can be reversed and advanced in a second direction until a second change in the limit sensor state is detected. The stepper motor can then be advanced in the second direction a predetermined number of steps associated with a full travel of the piston.

BACKGROUND

Coagulation monitoring devices are used to test a patient's bloodbefore, during and after procedures such as cardiac surgery,cardiovascular surgery, cardiac catheterization, electrophysiology,extracorporeal membrane oxygenation, hemodialysis, etc., to test thepatient's response to anti-coagulant medications such as:

-   -   Heparin    -   Vitamin K antogonists such as Warfarin (Coumadin)    -   Novel oral anticoagulants such as dabigatran, rivaroxaban, and        apixaban.

Anticoagulants are a class of drugs that work to prevent coagulation(clotting) of blood. It is important for each patient to be administeredthe amount and type of anti-coagulant that is appropriate for his/herindividual physiology. Too large an amount of anticoagulants can causeuncontrolled bleeding. Too small an amount of anticoagulants can causethrombosis (blood clotting), which can lead to heart attack (acutemyocardial infraction), or stroke.

Some known point-of-care (POC) coagulation monitoring devices operate bypumping a predefined quantity of blood from a sample well into a testchamber of a cuvette. The test chamber of the cuvette can contain anactivator such as silica, kaolin, diatomaceous earth, etc. Once in thetest chamber, the pump can move the sample back and forth at apredetermined rate and monitor for clot formation. For example, opticaldetectors can be operable to detect a decrease in sample mobility, whichcan be indicative of clot formation.

Known POC coagulation monitoring devices suffer from a number ofdeficiencies, including inaccurate pumps, high pump current draw, excesspump heat, and difficulties visualizing clot formation. Clotting timemeasurement is a critical measurement in a number of scenarios,including treatment of stroke victims and pre-operative care. Therefore,a need exists for improvements in coagulation monitoring devices.

Platelet function tests are used to assess the ability of a patient'splatelets to be activated via a specific pathway. This allows a medicalprofessional to evaluate a patient's response to P2Y12 inhibitors suchas thienopyridine's including clopidogrel (Plavix®) and prasugrel(Effient®) which are prescribed in cases of acute coronary syndrome(ACS) such as heart attack (acute myocardial infarction) and chest pain(angina). Platelet function tests can also measure activation from avariety of agonists such as arachidonic acid, epinephrine, collagen,etc.

Some known POC platelet function devices operate by pumping a predefinedquantity of blood from a blood tube into one or more test chambers.These devices may be turbidimetric based optical detection systems,which measure platelet induced aggregation. For example, each testchamber can be imaged via an independent optical sensor illuminated by adedicated emitter. The reagent is formulated to measure plateletaggregation mediated by a specific pathway (P2Y12, Arachadonic Acid,llb/llla). Light transmittance increases as activated platelets bind andaggregate fibrinogen coated beads. The instrument measures this changein optical signal and reports results in test specific Reaction Units(PRU, ARU, or PAU).

Known POC platelet function devices suffer from deficiencies similar tothose described above with reference to POC coagulation monitoringdevices, including inaccurate pumps, high pump current draw, excess pumpheat, and difficulties visualizing platelet aggregation. Individualresponse to p2Y12 inhibitors is variable and adequate plateletinhibition is not assured using a common empirical dose. For example,the literature reports as many as 30% of patients do not respond toPlavix. Platelet function testing is therefore a critical measurement toensure that each patient receives an effective dose of appropriatedrugs. Therefore, a need exists for improvements in platelet functiondevices. In some instances, embodiments described herein can be suitablefor improving platelet function devices and/or coagulation monitoringdevices.

SUMMARY

Some embodiments described herein relate to a method of operating apump, such as a pump of a coagulation monitoring device or a plateletfunction device, that can reduce or eliminate backlash errors andimprove pumping accuracy and accuracy of test results. Known pumps andknown methods of operating pumps are subject to backlash errorsassociated with changes in direction of the piston. When a pump motorchanges direction, the piston may not immediately respond, which cancause significant pumping errors. In instruments such as coagulationmonitoring devices and/or platelet function devices, pumping errors cansignificantly reduce the accuracy of test results.

According to an embodiment described in the present application, amethod of operating a pump can include advancing a stepper motor one ormore additional steps in a first direction after detecting a firstchange in a first limit sensor state corresponding to a piston and/orsample reaching an end of its travel in a first direction. Similarlystated, the stepper motor can be configured to “overshoot” (or attemptto overshoot) the first limit sensor after the limit sensor indicatesthat the piston and/or sample has reached the end of its travel. Afteradvancing the stepper motor the additional step or steps in the firstdirection, the stepper motor can be reversed and advanced in a seconddirection until a second change in the first limit sensor state isdetected. Similarly stated, the stepper motor can be advanced in thesecond direction until the first limit sensor indicates that the pistonand/or sample has begun to move away from it. The stepper motor can thenbe advanced in the second direction by either a predetermined number ofsteps associated with a full travel of the piston or until a firstchange in a second limit sensor state is detected. In this way, themethod can include verifying that any backlash error has been resolvedor overcome before the predetermined number of steps, associated with anappropriate and/or consistent travel of the piston and/or sample areapplied, which can improve pumping accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a pump, according to an embodiment.

FIG. 2 depicts a piston seal, according to an embodiment.

FIG. 3 depicts a finite element analysis of the piston seal of FIG. 2disposed within a pump housing.

FIG. 4 is a flowchart of a method of improving pumping accuracy,according to an embodiment.

FIG. 5 an optical system suitable for detecting clot formation,according to an embodiment.

FIGS. 6A-6C depict optical diffusers, according to various embodiments.

FIG. 7 depicts optical system within a coagulation monitoring device,according to an embodiment.

FIG. 8 is a schematic illustration of multiple coagulation monitoringdevices suitable for being managed via browser-based configurationmanager, according to an embodiment.

FIG. 9 illustrates a user interface of a browser-based configurationmanager, according to an embodiment.

DETAILED DESCRIPTION

Some embodiments described herein relate to methods of operating a pump,such as a piston pump driven by a stepper motor. The pump can be aportion of a medical device, such as a POC coagulation monitoring deviceor a platelet function device. Measurements produced by such devices canbe sensitive to small pumping errors. Similarly stated, maintainingprecise control of pump travel in such devices can be important toproducing accurate data.

One known method for operating a pump is to advance a stepper motor apredetermined number of steps in a first direction, then advancing thestepper motor the predetermined number of steps in the second directionand then repeating. Such a method assumes that with an equal number ofsteps applied, the piston travels equal distances in both the firstdirection and the second direction. A second known method for operatinga pump is to advance a stepper motor in a first direction until a firstlimit sensor is tripped, then advancing the stepper motor in a seconddirection until a second limit sensor is tripped and then repeating. Theassumptions underlying these known methods, however, are faulty. Pumpscan experience backlash errors when changing direction, resulting inmotor steps that do not move the piston. In addition, pistons canovershoot limit sensors, resulting in larger piston travel thanindicated by limit sensor. Some embodiments described herein relate tomethods of operating pumps that reduce and/or eliminate backlash error,improve the consistency of piston stroke length, and/or identify pumpingerrors which can decrease the accuracy of data and/or can be indicativeof a malfunction.

Some embodiments described herein relate to a method of operating apump. The pump can be fluidically coupled to a test device and used tomove a sample in the test device. In some embodiments, the test devicecan be a cuvette and/or can be disposable. An instrument containing thepump and test device can include a first limit sensor and a second limitsensor. For ease of description, the first limit sensor can beconfigured to sense when a sample within the test device and/or thepiston reach a fixed position at a “front” end portion of the testdevice and/or a “front” end portion of the pump. The second limit sensorcan configured to sense when the sample within the test device and/orthe piston reach a fixed position at a “back” end portion of the testdevice and/or on a “back” end portion of the pump. It should beunderstood that this is for ease of description only, and that the firstlimit sensor can be located on the back end portion of the test deviceand/or pump and the second limit sensor can be located on the front endportion of the test device and/or pump. Similarly stated, the firstlimit sensor and the second limit sensor can be located at fixedpositions at opposite end portions of the test device and/or pump andconfigured to change state when the piston and/or sample reach fixedpositions. In this way, the first limit sensor and the second limitsensor can collectively be configured to detect when the piston and/orsample has traveled an appropriate distance for the test being performedby the instrument.

According to one embodiment, a method can include detecting a firstchange in the state of the first limit sensor. The first change in thestate of the first limit sensor can indicate that the piston and/orsample has moved away from the fixed position and/or front end portionof the test device and/or pump on its way to the back end portion of thetest device and/or pump. The stepper motor can be advanced in thebackwards direction until a first change in the state of the secondlimit sensor is detected. The first change in the state of the secondlimit sensor can indicate that the sample and/or piston has reached theback end portion of the test device and/or pump. While the stepper motoris advanced in the backward direction (e.g., before the first change inthe state of the second limit sensor is detected), the number of stepstaken by the motor between the change in the first limit sensor statebeing detected and the first change in the state of the second limitsensor state can be counted and/or recorded. After the first change instate of the second limit sensor is detected, the stepper motor can beadvanced at least one additional step in the backward direction beforereversing the stepper motor and advancing the stepper motor in theforward direction. The stepper motor can then be advanced in the forwarddirection until a second change in state of the second limit sensor isdetected. The second change in state of the second limit sensor canindicate that the sample and/or piston has moved away from the back endportion of the test device and/or pump on its way to the front endportion of the test device and/or pump. After the second change in stateof the second limit sensor is detected, the stepper motor can beadvanced in the forward direction until a second change in the state ofthe first limit sensor is detected and/or until the number of steps thatwas counted and/or recorded between when the first change in the firstlimit sensor state was detected and when the first change in the stateof the second limit sensor state was detected. The number of pump stepscounted and/or recorded between the first change in the first limitsensor state and the first change in the second limit sensor state canbe compared to the number of pump steps counted and/or recorded betweenthe second change in the second limit sensor state and the second changein the first limit sensor state. If a difference between the number ofpump steps counted and/or recorded between (1) the first change in thefirst limit sensor state and the first change in the second limit sensorstate and (2) the number of pump steps counted and/or recorded betweenthe second change in the second limit sensor state and the second changein the first limit sensor state exceeds a threshold, an error can bereported.

According to another embodiment, a method can include advancing astepper motor one or more additional steps in a first direction afterdetecting a first change in a first limit sensor state corresponding toa piston and/or sample reaching an end of its travel and/or an endportion of a pump and/or test device in a first direction. Similarlystated, the stepper motor can be configured to cause the piston and/orsample “overshoot” (or attempt to overshoot) the first limit sensorafter the first limit sensor indicates that the piston and/or sample hasreached the end of its travel and/or reached an end portion of the pumpand/or test device. After advancing the stepper motor the additionalstep or steps in the first direction, the stepper motor can be reversedand advanced in a second direction until a second change in the firstlimit sensor state is detected. Similarly stated, the stepper motor canbe advanced in the second direction until the first limit sensorindicates that the piston and/or sample has begun to move away from it.The stepper motor can then be advanced in the second direction apredetermined number of steps associated with a full travel of thepiston and/or until the sample causes a second limit sensor to changestate.

According to another embodiment, a method can include recording a numberof steps taken by a stepper motor during a first transit from a first(e.g., front) limit sensor to a second (e.g., back) limit sensor. When afirst change in a state of the back limit sensor is detected, which canindicate that the piston has reached the back of the pump and/or asample has reached an back end portion of a test device, the steppermotor can be advanced one or more additional steps to move the pistonand/or sample towards the back of the pump/test device. Similarlystated, the stepper motor can be configured to overshoot (or attempt toovershoot) the back limit sensor. The stepper motor can then be reversedand advanced to move the piston and/or sample towards the front of thepump/test device. After a second change in the back limit sensor isdetected, which can indicate that the piston and/or sample has begun tomove towards the front of the pump/test device, the stepper motor canadvance the number of steps recorded when the stepper motor moved thepiston from the front limit sensor to the back limit sensor. Similarlystated, after the back limit sensor changes state to indicate that thepiston and/or sample has begun to move, which may only occur after anybacklash has been resolved and/or overcome, the stepper motor canadvance the same number of steps moving the piston and/or sample fromthe back of the pump/test device to the front of the pump/test device aswas recorded when the piston and/or sample moved from the front of thepump/test device to the back of the pump/test device. In an alternativeembodiment, after the second change in the back limit sensor isdetected, the stepper motor can advance until a change in the frontlimit sensor is detected.

FIG. 1 depicts a pump 100, according to an embodiment. The pump 100 canbe operable to pump a predefined quantity of blood from a sample wellinto a test chamber of a cuvette and/or move blood back and forth withina test chamber of a cuvette. The pump 100 includes a motor 110, a pumphousing 120, and a piston 130.

In some embodiments, the motor 110 is a stepper motor, but the motor 110can be any other suitable motor. The motor 110 can be coupled to thepiston 130 via a motor shaft 115. The motor shaft 115 can be coupled tothe piston 130 via a threaded connection to an adapter 125 having ananti-rotation feature 127 including a permanent magnet. Thus, the motor110 and the adapter 125 can collectively form a linear motor such thatextension and retraction of piston 130 can be effectuated by rotation ofthe motor shaft 115. In embodiments where the motor 110 is a steppermotor, the linear displacement of the piston 130 can be preciselycontrolled via the number of pulses applied to the motor 110. Inaddition or alternatively, positional sensors 150, such as Hall effectsensors, can be operable to monitor the position of the adapter 125,which can provide confirmation that the piston 130 has moved.

The piston 130 can travel within the pump housing 120 and a piston seal135 can create a substantially fluid-tight seal against the interiorwall 122 of the interior bore of the pump housing 120. For example andas described in further detail herein, the piston seal 135 can beovermolded such that, in an unbiased configuration, the piston seal hasa larger diameter than the diameter of the pump housing 120 defined bythe interior wall 122. Within the pump housing 120, at least a portionof the piston seal 135 can deform such that the substantiallyfluid-tight seal is maintained. Thus, when the piston 130 moves withinthe pump housing 120, fluid (such as blood) can be moved into or out ofthe pump housing 120 via an outlet 160.

As discussed above, known pumps used for POC coagulation monitoringdevices and/or platelet function devices suffer from a number ofdrawbacks. In particular, the amount of torque required to move thepiston in some known pumps (and the accompanying power draw and wasteheat produced) can be unacceptably high. For example, some known pumpsmaintain a seal between a piston and an interior wall of a pump housingusing an o-ring or similar gasket that is compressed against theinterior wall according to Gland design. When the Gland design is used,the compression of the gasket increases the torque required to move thepiston, and small variations within manufacturing tolerances cansignificantly increase the compression of the gasket and piston'sresistance to movement.

In some embodiments, such as shown in detail in FIG. 2, the piston seal135 can have two projections 138 or wings which elastically deflectwithin the pump housing 120, such that the radial force between thepiston seal 135 transmitted from the piston seal 135 to the piston 130is reduced as compared to a Gland design. As a result, decreased torquesrelative to the Gland design can be effective to move the piston 130. Inaddition or alternatively, grease or other suitable lubricant can bedeposited between projections 138, further reducing friction, powerconsumption, and/or waste heat while maintaining and/or improving afluid-tight seal.

FIG. 3 is a finite element analysis of a piston seal 235 forming a sealagainst an interior wall 222 of a pump housing 220. The piston seal 235,the pump housing 220, and the interior wall 222 can each be similar tothe piston seal 135, the pump housing 120, and the interior wall 122shown in FIGS. 1 and 2 and discussed above. As shown, elasticdeformation of the piston seal 235, particularly of wings 238, producesthe sealing force between the seal 235 and the inner wall 222. Region239 at the root of wing 238 illustrates this elastic deformation. Knowngaskets, such as quadrings, do not produce such radial flexion. Inparticular, the length of wings 238 relative to the clearance betweenpiston 230 and inner wall 222 differs from known gaskets. For example,in one embodiment, each wing 238 can have a length of 0.123approximately (e.g., +/−10%) inches, a base 236 of the gasket can have awidth of approximately 0.080 inches. A distance between the locations atwhich the wings 238 contact the inner wall 222 can be approximately0.100 inches. Seal 235 can differ from known gaskets, which aretypically compressed such that induced stresses are transmitted throughthe central region of the gasket (e.g., a geometric center), rather thanbeing substantially confined to the wings 238 and roots 239, as shown inFIG. 3. For example, in some embodiments, a central portion of seal 235(e.g., a geometric center) may experience stresses and/or strains lessthan 10% of the maximum stresses and/or strains, which are concentratedin wings 238. In some instances, the maximum stress of piston seal 235can be approximately 22 psi, which can be substantially lower than ano-ring or quad-ring compressed according the Gland design, which canexperiences stress of 200 psi or more.

In addition, obtaining an accurate sample volume and/or precise controlover moving the sample while performing a blood clotting measurement orplatelet function measurement can be important factors in obtaining anaccurate and/or reproducible measurement. Precise control of themovement and/or position of a piston and/or a sample driven by thepiston can influence the accuracy of the test. In particular, with someknown pumps, errors can accumulate at the beginning and/or end of pistonmovement, when the piston and/or sample reaches the end of its travel,and/or when the piston and/or sample changes direction. For example,some known pumps are susceptible to backlash error in which the motortakes several steps before the piston and/or sample begins to move,particularly when the pump changes direction. Some embodiments describedherein relate to a method for reducing or eliminating such backlasherror. FIG. 4, is a flow chart of a method for reducing or eliminatingpump backlash error. Such a method can be performed by a pump, such aspump 100 shown and described above. In addition or alternatively, such amethod can be a computer implemented method, stored in a memory and/orexecuted by a processor, which can be electrically coupled to a pumpmotor and/or pump position sensor.

At 410, a change in a state of a first limit sensor can be detected. Thechange of the state of the first limit sensor can indicate that thepiston has reached a fixed location at an end-portion its travel and/orthat a sample being driven by the piston has reached a fixed locationwithin a test device. After the change in the state of the first pistonlimit sensor is detected, at 410, the motor can take one or moreadditional steps, at 415, before the motor direction is reversed, at420. Similarly stated, the motor and piston can be configured toovershoot (or attempt to overshoot) the first limit sensor.

After the motor reverses, at 420, another change in the first limitsensor state can be detected, at 425. The change in state of the firstlimit sensor, at 425 can indicate that the piston and/or sample ismoving and any extra motor steps needed to overcome a backlash have beensuccessful. Each step after the change in the first limit sensor stateis detected, at 425, can be counted until a change in a second limitsensor state is detected, at 440. The change in the second piston limitsensor state detected, at 440, can be an indication that the piston hasreached a fixed location at an end-portion its travel and/or that asample being driven by the piston has reached a fixed location within atest device in the direction opposite the first limit sensor. Similarlystated, the first limit sensor can be configured to change state whenthe piston is retracted and the second limit sensor can be configured tochange state when the piston is extended, or vice versa. The first limitsensor and the second limit sensor can each be configured to detect whenthe piston and/or the sample has reached a mechanical and/orpreconfigured limit.

The number of steps between the change in the first limit sensor statebeing detected, at 425, and the change in the second limit sensor statebeing detected, at 440, can be recorded (e.g., stored in memory) at 445.

After the change in the state of the second limit sensor is detected, at440, before reversing direction, at 455, the motor can take one or moreadditional steps, at 450. Similarly stated, the motor and piston can beconfigured to overshoot (or attempt to overshoot) the second limitsensor.

After the motor reverses, at 455, another change in the second limitsensor state can be detected, at 460. The change in state of the secondlimit sensor, at 460 can indicate that the piston and/or sample ismoving and any extra motor steps needed to overcome a backlash have beensuccessful. At 465, the number of steps recorded at 445 can be applied.In this way, the method described with reference to FIG. 4 can beoperable to assure that the same number of motor steps is applied duringeach stroke of the piston after any potential backlash has beenresolved.

This technique can be repeated in a similar fashion, for example, untila clot is detected. For example, after the recorded number of steps hasbeen applied at 465, one or more additional steps can be applied, at415, before the motor reverses direction, at 420. After the motorreverses direction, at 420, the transit step counter can be reset tozero, at 430, after a change in the first limit sensor is detected, at425. The change in the state of the first limit sensor state canindicate that the piston and/or sample is moving towards the secondlimit sensor and any potential backlash has been resolved. The samenumber of steps as was originally recorded at 445 can be applied suchthat the piston travels the same distance with each stroke.

It is expected that each time the recorded number of steps is applied alimit sensor will change states. In some instances, if a limit sensorchanges state before the recorded number of steps has been applied or ifa limit sensor does not change state after the recorded number of stepshas been applied, an error signal can be produced. For example, in aninstance where a limit sensor changes state before the recorded numberof steps are applied, a difference between the recorded number of stepsand the number of steps applied before the limit sensor changed statescan be computed. If the difference is greater than a threshold value, anerror can be reported. Similarly, in an instance where the recordednumber of steps is applied and a limit sensor has not changed states,surplus steps can be applied until a limit sensor state change isdetected. If the number of surplus steps is greater than a thresholdvalue, an error can be reported.

In addition or alternatively, the discrepancies in the number of stepsfrom the first limit sensor to the second position limit sensor can betabulated and an error signal can be produced if the discrepancies areabove a threshold value. For example, if a limit sensor changes statebefore the recorded number of steps has been applied, the routine can beshortened and one or more additional motor steps can be applied beforethe motor reverses direction and the number of unneeded steps can berecorded. Then, after the limit sensor changes state for a second timeindicating any backlash has been overcome and/or resolved, either theoriginal number of steps can be applied or the number of steps fromlimit sensor to limit sensor in the last stroke can be applied.Similarly, if the number of steps recorded at 445 are applied and nochange in limit sensor state is detected, additional steps can beapplied until a limit sensor state occurs and the number of additionalsteps required can be recorded.

As described above, the pump can continue to transit until a clot isdetected. A clot can be detected by imaging a chaplet of blood. Thechaplet of blood can be moved within a channel of a cuvette, testdevice, and/or any other suitable by a pump, such as the pump 100 shownand described above with reference to FIGS. 1 and 2 according to themethod described with reference to FIG. 4. In particular, the methoddescribed with reference to FIG. 4 can improve measurements of thetransit of the chaplet and half-transit measurements, improving theaccuracy of clotting time assays relative to methods that do not reduceor eliminate backlash errors.

FIG. 5 depicts an optical system 500 suitable for detecting clotformation. The optical system 500 includes an optical detector 1, alight source 3, and an optical diffuser 4. Some known POC coagulationmonitoring devices use a light source and an optical detector todetermine when a clot has formed. Known devices, however, suffer from anumber of deficiencies. In particular, the light source of known devicestypically directly illuminates a target, which can produce undesirableglare resulting in visual artifacts when the target is imaged by anoptical detector, decreasing measurement accuracy. In addition oralternatively, relatively large geometries may be employed by knowndevices in an effort to reduce glare (e.g., the light source may bepositioned a relatively large distance from target). Such largegeometries increase the size of the instrument and may make a handhelddevice impossible or impracticable.

The optical system 500 remedies the deficiencies of known instruments byilluminating a target 6 (e.g., containing a chaplet of blood) withdiffuse light, which allows the instrument to maintain a compactgeometry and relatively small overall size. As shown, a diffuser 4 ispositioned in front of light source 3. The diffuser can be constructedof light colored (e.g., white) and/or translucent plastic or any othersuitable material. In this way, light produced by the light source 3,which can be a light emitting diode, laser, or any other suitable sourceof illumination, can be scattered by diffuser 3 and/or light emanatingfrom the light source 3 can be prevented from directly illuminatingtarget 6, which can reduce or eliminate glare on the target 6.

The target 6 can then be imaged by the optical detector 1, which can befor example, a charge coupled device, a complementary metal-oxidesemiconductor, etc. The optical detector 1 can optionally include one ormore lenses. Similarly stated, the optical detector 1 can be a camera.Mirrors 2 and 5 can reflect an image of target 6 onto optical detector1, which can increase the focal length and/or field of view of thecamera (e.g., such that an entire length of a substantial portion of thelength of the target 6 can be imaged) while maintaining a compact devicesuitable for hand-held operation. FIG. 6A depicts the diffuser 3,according to an embodiment. FIGS. 6B and 6C depict diffusers accordingto alternate embodiments. The diffusers depicted in FIGS. 6B and 6Cdemonstrate that diffusers can have alternate geometries, such asoptional side panels 610, variations in dispersion arm 620 angles,and/or variations in upper diffuser surface angles.

FIG. 7 depicts optical system 100 within a POC coagulation monitoringdevice 700, according to an embodiment.

POC coagulation monitoring devices, such as the coagulation monitoringdevice 700 shown and described above with reference to FIG. 7, caninclude hardware and/or software (stored in memory and/or executing on aprocessor) operable to be configured to run one or more tests, executeone or more tests autonomously or semi-autonomously, log test results,collect patient identifiers, operator identifiers, reagent identifiers,and so forth. Known POC coagulation monitoring devices and/or plateletfunction devices are generally stand alone instruments and aninstitution (e.g., a hospital) may have a large number of such devices.In known systems configuration of each device may be performed byconnecting the device to a single computer via a serial or similarconnection. A risk therefore exists that different instruments may beconfigured differently, reducing reproducibility. Alternatively, someknown systems administer multiple devices using a central server thatcan configure multiple instruments. A central server, however, presentsa single point of failure and increases capital and operational costs,system complexity, and ongoing administration and support. A needtherefore exists for an instrument configuration manager that canconfigure multiple devices without relying on a central serverarchitecture.

The POC coagulation monitoring devices and/or platelet function devicesdescribed in the present application can include a browser-basedconfiguration manager. For example, a browser-based configurationmanager can be stored in memory and/or executed by a processor of a POCcoagulation monitoring device. The browser-based configuration managercan be a web application.

As shown in FIG. 8, the browser-based configuration manager residing onone or more coagulation monitoring devices 810 can be operable tocommunicate with one or more desktop computers 820, laptop computers830, tablet computers 840, smartphones 850, and/or any other suitablecomputing entity (also referred to herein as compute device(s)) via awireless gateway 860 (e.g., a WiFi access point) and/or via a wirednetwork 870 (e.g., an Ethernet network, an intranet, the Internet,etc.). One or more compute devices can be configured to communicate withthe browser-based configuration manager residing on the coagulationmonitoring devices 810. For example, a web browser (stored in memoryand/or executing on a processor) residing on a compute device can beoperable to broadcast, narrowcast, and/or multicast configurations toone or more of the coagulation monitoring devices 810. In this way, oneor more coagulation monitoring device 810 can be configured remotelyusing a robust web interface, for example, by a clinician and/oradministrator. Such a web interface may be more intuitive and/orflexible than an input/output interface of a relatively small handheldcoagulation monitoring device. Moreover, the browser-based configurationmanager can eliminate the need for a central server or a special-purposeprogram or application to be installed on compute devices, which may bediscouraged and/or prohibited by institutional information technologypolicies.

FIG. 9 illustrates a user interface of the browser-based configurationmonitor, which is shown being executed (by a processor) of a computedevice via Microsoft's® Internet Explorer® browser. As shown, thebrowser-based configuration monitor can be operable to interact withand/or monitor the status of any number of coagulation monitoringdevices 810, which are shown identified by IP address, but can beidentified by any other suitable identifier such as location, user- oradministrator-assigned identifier, model number, serial number, etc. Thestatus of each coagulation monitoring device can be displayed, forexample, by color coding identifiers (e.g., red for disconnected, greenfor connecting, blue for selected, etc.) or any other suitabletechnique.

Using the browser-based configuration monitor, a user can add or removedevices from being monitored and/or select one or more devices toreceive a configuration update. When configuring devices, parameters canbe set using the browser interface and transmitted to each coagulationmonitor device 810, which can be remote from the compute device. Ininstances where multiple coagulation monitoring devices 810 areconfigured, the browser-based configuration manager can assure that eachselected coagulation monitoring devices 810 is configured with the sameparameters.

The browser-based configuration monitor can be operable to configure oneor more coagulation monitoring devices 810 in a manual, semi-automatic,or automatic process. For example, in a manual process, a user canselect one or more coagulation monitoring devices 810, supply theappropriate parameters, and transmit the parameters to the one or morecoagulation monitoring devices 810, for example, by clicking a button.In an automatic process, all connected devices or a subset of alldevices can be displayed and updated with the latest configuration. Forexample, all devices in a cardiac catheterization lab can beautomatically selected and updated with the most recent cardiaccatheterization lab configuration.

In addition or alternatively, configuration settings (e.g., set by aremote compute device via the browser-based configuration monitor) canbe viewed and/or modified at a coagulation monitoring device. Similarlystated, a clinician can override or modify a group setting for aparticular test using the input/output interface of the coagulationmonitoring device 810 and/or can modify a setting for a particularcoagulation monitoring device using the clinician's personal smartphone850 or other compute device.

Some known medical devices can perform a Power On Self Test (POST) toverify instrument functionality when devices are turned on. Many medicaldevices, however, are not “powered on” during routine operation. Forexample, a medical device may be powered up and not powered down orunplugged for hours or days. When a device is in service for an extendedperiod of time since the most recent POST, a risk develops that one ormore hardware components or systems has failed and/or that memory hasbecome corrupted between the POST and when an instrument is used toanalyze a sample. Known instruments perform POSTs by verifying theoverall functionality of the system, for example, by performing asimulated sample analysis or dry run. Such known POSTs generally take asubstantial period of time (e.g., 45 seconds to several minutes) toperform. Performing such a POST in between sample analyses or before asample is analyzed is not generally feasible. A need therefore exists toverify the operation of an instrument prior to a sample analysis withoutintroducing lengthy delays or down time.

In some embodiments, a medical instrument, such as the POC coagulationmonitoring devices and/or platelet function devices described above, canperform an electronic quality control check of the device's measurementpathway(s) and critical electronics, immediately prior to analyzing asample. Such an electronic quality control check can test componentsindividually and/or in parallel, rather than testing the system as awhole, such as by performing a dry run, as is typical for known POSTs.In this way, the time to verify instrument reliability can be reducedsignificantly to, for example, ten seconds or less.

The electronic quality control check can verify the operation of theinstrument by testing internal voltages, analytic firmware (e.g., via acyclic redundancy check), assay definition file (e.g., via a cyclicredundancy check), calibration (e.g., via a cyclic redundancy check),factory settings (e.g., via a cyclic redundancy check), batteries,camera, the operation of the real time clock, external voltage supply,serial communications, and/or any other suitable hardware, software,and/or subsystems.

During an electronic quality control check a quality control program(stored in memory and/or executing on a processor) can receiveindependent feedback from tested element(s). For example, DC voltage canbe fed, via independent inputs, to a quality-control checkanalog-to-digital converter, which can measure the voltage and determine(e.g., individually) if each DC voltage is within acceptable ranges(e.g., using software stored in memory and/or executing on a processor).In addition or alternatively, tested elements can be cross checkedagainst each other. For example, an output from a camera can be analyzedwith field of view illumination turned on and with field of viewillumination turned off. In this way, a malfunction in either the cameraor the illumination can result in an error being generated if, forexample, the output of the camera does not change as expected when theillumination is turned on.

In the event of an error, the user can be notified via the POCcoagulation monitor input/output and/or a signal can be sent to abrowser-based or other suitable configuration monitoring system. In someinstances, the coagulation monitor can prevent further operation of thedevice until all parameters and/or critical parameters are withinpredetermined operational ranges.

Some embodiments described herein relate to a computer storage productwith a non-transitory computer-readable medium (also can be referred toas a non-transitory processor-readable medium) having instructions orcomputer code thereon for performing various computer-implementedoperations. The computer-readable medium (or processor-readable medium)is non-transitory in the sense that it does not include transitorypropagating signals per se (e.g., a propagating electromagnetic wavecarrying information on a transmission medium such as space or a cable).The media and computer code (also can be referred to as code) may bethose designed and constructed for the specific purpose or purposes.Examples of non-transitory computer-readable media include, but are notlimited to: magnetic storage media such as hard disks, floppy disks, andmagnetic tape; optical storage media such as Compact Disc/Digital VideoDiscs (CD/DVDs), Compact Disc-Read Only Memories (CD-ROMs), andholographic devices; magneto-optical storage media such as opticaldisks; carrier wave signal processing modules; and hardware devices thatare specially configured to store and execute program code, such asApplication-Specific Integrated Circuits (ASICs), Programmable LogicDevices (PLDs), Read-Only Memory (ROM) and Random-Access Memory (RAM)devices. Other embodiments described herein relate to a computer programproduct, which can include, for example, the instructions and/orcomputer code discussed herein.

Examples of computer code include, but are not limited to, micro-code ormicro-instructions, machine instructions, such as produced by acompiler, code used to produce a web service, and files containinghigher-level instructions that are executed by a computer using aninterpreter. For example, embodiments may be implemented using Java,C++, or other programming languages (e.g., object-oriented programminglanguages) and development tools. Additional examples of computer codeinclude, but are not limited to, control signals, encrypted code, andcompressed code.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. For example, some aspects described in the presentapplication are described with respect to POC coagulation monitoringdevices. It should be understood that some aspects described herein haveapplicability to applications other than POC coagulation monitoringdevices. In particular, the diffuser described above with reference toFIGS. 5-7 or a similar diffuser can be used in a platelet functioninstrument or any other suitable instrument in which an optical detectorimages a target illuminated by a light source positioned a relativelyshort distance from the target. As another example, the browser-basedconfiguration manager and/or the electronic quality control checkdescribed above can be implemented by any suitable device, such as aplatelet function instrument.

Where methods and/or schematics described above indicate certain eventsand/or flow patterns occurring in certain order, the ordering of certainevents and/or flow patterns may be modified. Additionally certain eventsmay be performed concurrently in parallel processes when possible, aswell as performed sequentially. While the embodiments have beenparticularly shown and described, it will be understood that variouschanges in form and details may be made.

Although various embodiments have been described as having particularfeatures and/or combinations of components, other embodiments arepossible having a combination of any features and/or components from anyof embodiments where appropriate.

What is claimed is:
 1. A method to reduce or eliminate pump backlash errors, comprising: providing a system comprising a pump having a stepper motor coupled to a piston, said system further comprising a first limit sensor displaced apart from a second limit sensor; advancing, with the motor, the piston in a forward direction in the pump; detecting a first change in the first limit sensor state to indicate that the piston has reached a fixed forward location at an end-portion of its forward travel in the pump; using the motor to advance the piston one or more additional steps in the forward direction beyond the fixed forward location after the first change in the first limit sensor state is detected; using the motor to advance the piston in a rearward direction opposite the forward direction after the one or more additional steps; and, detecting a second change in the first limit sensor state indicating that the piston is moving in the rearward direction from the fixed forward location in the pump and that backlash errors associated with changes in direction of the piston have been reduced or eliminated.
 2. The method of claim 1, further comprising: detecting the second change in the first limit sensor state after advancing the stepper motor in the rearward direction a portion of the number of steps; and reporting an error based on a difference between the number of steps and the portion of the number of steps being greater than a threshold.
 3. The method of claim 1, further comprising: counting a number of steps while advancing the piston in the rearward direction until a first change in a second limit sensor state is detected indicating that the piston has reached a fixed rearward location at an end-portion of its rearward travel in the pump; using the motor to advance the piston one or more additional rearward steps in the rearward direction beyond the fixed rearward location after the first change in the second limit sensor state is detected; using the motor to advance the piston in the forward direction after the one or more additional rearward steps; and detecting a second change in the second limit sensor state after advancing the piston in the forward direction indicating that the piston is moving in the forward direction from the fixed rearward location in the pump and that backlash errors associated with changes in direction of the piston have been reduced or eliminated.
 4. The method of claim 1, further comprising advancing the stepper motor in the forward direction the number of steps after advancing the stepper motor in the rearward direction the number of steps.
 5. A non-transitory computer readable media having software encoded thereon, the software configured to to cause the processor to: detect a first change in a first limit sensor state corresponding to a piston, driven by a stepper motor, reaching an end of its travel in a forward direction; advance the piston one or more additional steps in the forward direction after detecting the first change in the first limit sensor state; reverse the piston in a rearward direction after the one or more additional steps; detect a second change in the first limit sensor state; and reverse the piston in the rearward direction a predetermined number of steps associated with a full travel of the piston.
 6. The non-transitory computer readable media of claim 5, wherein the software is further configured to the processor to: detect a change in a second limit sensor state after the stepper motor is advanced in the rearward direction the predetermined number of steps associated with the full travel of the piston.
 7. The non-transitory computer readable media of claim 5, wherein the software is further configured to cause the processor to: detect a change in a second limit sensor state after the stepper motor is advanced in the rearward direction the predetermined number of steps associated with the full travel of the piston; and advancing the piston by the stepper motor in the forward direction the predetermined number of steps associated with the full travel of the piston after detecting the change in the second limit sensor state.
 8. A method to reduce or eliminate pump backlash errors, comprising: (i) recording a number of steps taken by a stepper motor between a change in a first limit sensor state being detected and a change in a second limit sensor state being detected, during a transit of a piston driven by the stepper motor in a rearward direction from the first limit sensor to the second limit sensor; (ii) detecting a first change in said change in the state of the second limit sensor; (iii) advancing the piston one or more additional steps by the stepper motor in the rearward direction; (iv) advancing the piston in a forward direction opposite the rearwared direction until a second change in the state of the second limit sensor is detected; (v) advancing the piston in the forward direction the number of steps by the stepper motor after the second change in the state of the second limit sensor is detected; and (vi) advancing the piston in the rearward direction the number of steps by the stepper motor after the piston has been advanced the number of steps in the forward.
 9. The method of claim 8, further comprising: advancing the piston in the rearward direction until the change in the state of the first limit sensor is detected before advancing the piston in the rearward direction the number of steps by the stepper motor.
 10. The method of claim 8, further comprising: detecting the first change in the state of the first limit sensor after advancing the piston in the forward direction the number of steps; advancing the piston an additional step in the forward direction after detecting the first change in the state of the first limit sensor; and advancing the piston in the rearward direction after advancing the piston the additional step in the forward until the second change in the state of the first limit sensor is detected before advancing the piston in the rearward direction the number of steps by the stepper motor.
 11. The method of claim 8, further comprising: advancing the piston an additional step in the forward direction before advancing the piston in the rearward direction the number of steps; and advancing the piston in the rearward direction until a change in the state of the first limit sensor is detected before advancing the piston in the rearward direction the number of steps.
 12. The method of claim 8, further comprising repeating the steps (i) through (vi).
 13. The method of claim 8, wherein the stepper motor is coupled to the piston, the stepper motor and the piston being components of a pump of a medical instrument.
 14. The method of claim 8, wherein: the stepper motor is configured to move the piston between the first limit sensor and the second limit sensor; and the piston is configured to move a volume of sample within a coagulation monitoring device or a platelet function test device. 